A clock is an instrument to indicate, keep, and coordinate time. The origin of the term is derived ultimately from the Celtic words clagan and clocca meaning “bell” and is evidence in the French word “cloche,” the Latin word “glocio,” the Saxon word clugga and the German word “glocke.” A silent instrument missing such a striking mechanism like a bell has traditionally been known as a timepiece, but today the term timepiece has become a broader term for devices keeping time. Watches are timepieces that are carried on one’s person and are typically understood to be different from immobile timepieces placed in rooms.
The timepiece is one of the oldest human inventions, meeting the need to consistently measure intervals of time shorter than the natural units: the day, the lunar month, and the year. Devices operating on several physical processes have been used over the millennia.
Sundials tell apparent sun time by displaying the position of the sun by shadow on a flat surface, while timepieces tell Mean Solar Time. Four times yearly Sundials and timepieces agree. However, the Sundial time is sometimes 16 minutes faster and sometimes 14 minutes slower than timepieces. This difference is known as “The Equation of Time.”
There are a range of duration timers, a well-known example being the hourglass. Water clocks, along with the sundials, are possibly the oldest time-measuring instruments. Candles were also used in ancient times as a device for measuring the passing of time by marking intervals along the length of the candle.
A major advance in the development of timepieces occurred in Europe around 1300 with the invention of the “escapement,” which allowed construction of the first mechanical timepieces using oscillating timekeepers like balance wheels. Spring-driven timepieces appeared during the 15th century and the use of the pendulum to keep time was invented in 1656, Dutch mathematician, astronomer, physicist and horologist Christiaan Huygens. The use of the pendulum rather than the foliot verge escapement was a giant step forward in timekeeping. In 1583 Galileo had demonstrated that successive beats of a pendulum always take place in the same length of time, regardless of the distance through which it swings.
An early prototype of timepieces with alarms was invented by the Greeks around 250 BC. The Greeks built a timepiece using water where the raising waters would both keep time and eventually hit a mechanical bird that triggered an alarming whistle. Another early alarm was a candle with a nail placed down in the wax. When the candle melted to the nail, it would fall into a tin pan and make a noise. The first alarm timing mechanism was invented by Levi Hutchins in New Hampshire in 1787. However, Hutchins’ ringing bell alarm could ring only at 4 am. In 1876 a mechanical wind-up alarm timepiece that could be set for any time was patented by Seth E Thomas.
Christiaan Huygens also invented a device of equal significance to the pendulum in the development of the watch. It is the spiral balance, also known as the hairspring (an invention also claimed, less convincingly, by Robert Hooke). This very fine spring, coiled flat, controls the speed of oscillation of the balance wheel. For the first time it was possible to make a watch which is reasonably accurate – and slim. This influenced fashion of the late 17th century as gentlemen were able to keep the time and slip their piece into a waistcoat pocket. About 50 years later, the electric timepiece was patented in 1840. The development of electronics in the 20th century led to timepieces with no moving parts at all.
Although the methods they use vary, all oscillating timepieces, mechanical and digital and atomic, work similarly and can be divided into comparable parts. They consist of an object that repeats the same motion over and over again, an oscillator, with a precisely constant time interval between each repetition, or ‘beat’. Attached to the oscillator is a controller device, which sustains the oscillator’s motion by replacing the energy it loses to friction, and converts its oscillations into a series of pulses. The pulses are then counted by some type of counter, and the number of counts is converted into convenient units, usually seconds, minutes, hours, etc. Finally, some kind of indicator displays the result in human readable form.
There are two major distinctions in timepieces: how they keep time and how they display time. The timekeeping element in every modern timepiece is a harmonic oscillator, a physical object (resonator) that vibrates or oscillates repetitively at a precisely constant frequency. This object can be a pendulum, a tuning fork, a quartz crystal, or the vibration of electrons in atoms as they emit microwaves. The components that you find in today’s wind-up watches have been around for centuries: a spring to provide the power, some sort of oscillating mass to provide a timebase, two or more hands, an enumerated dial on the face of the watch, and gears to slow down from the ticking rate of the oscillating mass and connect the mass and spring to the hands on the dial.
Analog timepieces usually display time using angles while digital timepieces display a numeric representation of time. Analog timepieces usually indicate time using angles. The most common timepiece face uses a fixed numbered dial or dials and moving hand or hands. It usually has a circular scale of 12 hours, which can also serve as a scale of 60 minutes, and 60 seconds if it has a second hand. Many other styles and designs have been used throughout the years, including dials divided into 6, 8, 10, and 24 hours.
Most digital devices use electronic mechanisms and LCD, LED, or VFD displays. For convenience, distance, telephony or blindness, auditory timepieces present the time as sounds. Over the last century, designers have created a variety of alternative display methods for both analog and digital formats.
The evolution of the technology of timepieces continues today, especially with the advent of mobile technology. For example, many people use their phones as their mobile timekeeper in place of watches. With the advent of the atomic clock, the ‘true’ standard time is broadcast via radio signal to which timepieces can be tuned to for the time, many timepieces these days don’t keep time but rather are ‘given’ the time and simply display it. The same is true for some internet-based time references used by devices. However, electronics like phones use their processors to keep time as a necessary component of their function.